Electric insulation board and method of making same



Patented Sept. 22, 1925.

UNITED STATES DANIEL HANSON BUTEEBLAND,

13., OF TBENTON, NEW JERSEY.

ELECTRIC INSULATION BOARD AND METHOD OF MAKING SAME.

No Drawing.

To all whom it ma concern:

Be it known that I, DANIEL MANSON SUTHERLAND, Jr., a subject of the King of Great Britain who has filed his first papers 6 and declared his intention of becoming a citizen of the United States), now resi ms at Trenton, in the county of Mercer an State of New Jersey, have invented certain new and useful Improvements in Electric 10 Insulation Boards and Methods of Making Same, of which the following is a specification.

This invention pertains to electric-insulation boards and bodies, and to the method of roducing the same.

he purposes sought and attained by the invention are the production of an inexpensive electric-insulation board or body of high insulating capacity, of desired color or 2 shade, and capable of receiving and maintaining any desired finish.

To these ends the invention consists in forming a sheet or body of pul or cellulose, combined with gilsonite, as ha tum, mineral itch, elaterite, resin, or ot er usual binder; rying the same to a suitable degree; then applying to its face or faces a thin coating or layer of a cellulose acetate varnish or lacquer produced with the aid of a suitable solvent and thinning agent; and subjecting the sheet or body to com ression and heat.

The primary purpose 0 the cellulose varnish or lacauer coating is to prevent the insulating bo y, board or other, from adhering to to the contactin faces of a press, mold, or

other structure in which the final compression and drying under heat are effected;

also to permit or facilitate the incorporation of any suitable pigment or coloring agent,

and to produce a surface which may be finished by the aid of sandpaper emery cloth,

or other abradant of suitab e fineness, or by bulfing or like treatment where a high polish as distin uished from a dead or flat finish,

is desire The boards or bodies so produced are also devoid of stickiness or tackiness,

and hence are not liable to adhere to one another, or to their wrappings, when packed or shipped.

No special form or construction of apparatus is required'in carrying out my process. On the contrary, usual types of presses,

molds, etc, for extracting surplus moistureand for shaping and compressing the body 55 and completely drying the same, may be em- Application filed November 6, 1923. Serial 1%. 678,221.

gloyed. After such final compression and rying the surface may be finished after the manner of finishin various woods and composltions, either t rou h the use of abraelves and powders suita le to the production of a smooth surface without high polish, or gloss, or a highly polished surface.

Better to explain the present invention, and to differentiate the method of treatment or manufacture from prior practice, it may be stated that in the process of manufacturing insulation boards composed of pulp and gi sonite or other binder, it is necessary to a compact the composition in a ress or mold provided with pressure hea s, plates or walls, one or more, capable of being heated and cooled in some convenient way. Where the composition contains gilsonite, or any one of a number of other binders. difiicult is experienced in compacting the compositlon owing to its stickiness or tendency to adhere to contacting surfaces. Various attempts have been made heretofore to prevent such adherence to the press or mold surfaces, but so far as I am aware they have failed to accomplish the desired result, and have likewise resulted in reducing a body the surface of which is itself sticky or tacky, and diflicult to finish satisfactorily or in a manner acceptable to the trade.

Various agents or compositions desi ed to overcome the-stated difiiculty have en found to impair the dielectric properties of the finished board. This is true, for instance, of collodion or nitrocellulose varnishes, since a short circuit or a flash-over is liable to cause combustion. Surface coatings consisting mainly of fatty acids, of linseed or china wood oil, or coatings similar to oil varnishes, prevent stickiness in some measure but fail to give a satisfactory finish or surface.

I have found through careful experimentation that varnishes or lacquers made from cellulose acetate dissolved in a suitable solvent give a film on the surface which prevents stickiness under combined heat and pressure, and at the same time, through close union with the pulp or cellulose body or composition, affords a surface that can be sanded or bufi'ed to a fine finish, either flat or of hi h polish.

It is desirable in many instances to im art to the board or body a de of flexiility, or a capability of being bent to 110 similar materials are used. The cellulose acetate varnish or lacquer unites, as above indicated, with the cellulose composition of the board or body, during compression and heating, and causes the color to penetrate or permeate said body to a greater or less depth, thus making a better commercial 1 product than would be produced if the coloring matter were confined to a thin surface film or coating.

As indicated, the selection of a proper cellulose acetate lacquer or varnish is important. I have found, for instance, that the hydracetate of cellulose gives better results than the triacetate of cellulose, because it is more stable than the latter and is more readily soluble in cheaper solvents. The principal solvents used are acetone and methylacetone, but the latter can be use successfully only in conjunction with hydracetate, as it will not, alone, completely dissolve the triacetate.

The proportion of solvent used depends upon the method of applying the lacquer. For example, when the lacquer is applie by dipping the board or article, it 15 expedient 'to employ twelve (12) parts of methylacetone to one (1) part of cellulose hydracetate, whereas but eight (8) parts of solvent to one (1) part of acetate are use when the coating is applied by means of a brush.

To prevent the film or coating from becoming brittle, use may be made of methyl ester of paratoluelsulphoneamide, triacetin, or triphenyl phosphate. The use of methyl ester of paratoluelsulphoneamide is preferred, as triacetin and triphen 1 phosphate give less satisfactory results. are must be taken in the use of an softening agent or solvent that the quantity employed be not excessive, as otherwise it emoresces on the surface of the product, causing a white or moldy appearance thereon. One (1) part of methyl ester of paratoluelsul honeamide to ten (10) parts of h dracellu ose is sufiicient to prevent britt eness and does not cause efllorescence, whereas one (1) part of said methyl ester to five (5) parts hydracetate causes efllorescence which materially mars the appearance of the product.

When desired, the hydracetate solution may be diluted through the addition of ethyl-alcohol and benzol, but such agents must be used only in limited quantity, as otherwise the hydracetate is thrown out of d or coloring matters employed, an

1 steps constitgite a ty ica procedure:

solution. A thinning composition composed of two (2) parts of methylacetone, one (1) part ethyl-alcohol, and one (1)- part of benzol g1ves satisfactory results. These proportions may be varied within reasonable limits without preci itating the hydracetate of cellulose out of t e solution, but undue variation must be avoided else such precipitation will occur.

To produce various colored surfaces, coloring matter may be added to the hydracetate solution in suitable quantity to give the de- 1 sired color or shade, but the pigment or colorin matter must be such as will withstand t 1e temperature of the heating plates, and be as stable as possible when subjected to strong light. For producing a black finish or color, nigrosine is the most suitable agent at present known to me. Carbon black maybe used, but is undesirable because the free carbon which it contains 1. impairs the insulating properties of the 1 class, or the source whence the cellulose is obtained, the binder employed and the relative roportions of cellulose and binder, the cellu ose acetate compositlon lacquer or varnish used as a coating for such body, the choice of solvents therefor, the igments (i the use or non-use of softening agents, as also their character. and quantity as related to the cellulose acetate composition.

As, a concrete .exam Ie the following 1. A sheet or bo y .is formed of pul composition comprising cellulose and gi sonite or other suitable and known hinder, the roportion of which binder may vary within the range now usual in the art.

2. The sheet or body so formed is sub stantially freed of-its liquid content, preferably b heavy pressure, and finally completel ried in any suitable way.

3. uy face or all faces of the board or body so dried is or are coated with the cellu-' lose acetate varnish, lacquer, or composition, by spraying or dipping, by means of a brush, or otherwise, as found expedient in any given situation. If it be desired to-impart any given color to the boardor ultimate product, such coloring matter or pigment is incorporated in the cellulose acetate. composition, and so a plied to the surface or surfaces coated. (gare should be taken that only sufiicient of the cellulose acetate preparation to be used to form a film between the board or body and the surface or surfaces with which an element of a pressure device of any. suitable type is later to contact. A film of approximately one onehundredth of an inch in thickness is usually sufiicient.

4. This coating is allowed to dr and the coated board or body is then su jected to heavy pressure in any suitable press or pressure device capable of being heated in such portion or portions as come into contact with the coated face or faces of the board or body, so that said board or body shall be sub ected simultaneously to pressure and to heat, and so also that those portions of the board or body subjected to heat shall be prevented by the cellulose acetate coating from adhering to the heated surfaces. This treatment is continued until the board or body is compacted to the desired density. The pressure is further maintained for a time, the steam or other heating agent is then cut off, and a cooling agent is substituted therefor in order to lower the temperature of the board or body while still under pressure and to prevent any war ing or distortion of such board or body w en relieved of pressure.

5. The compressed and dried board or body is now removed from the press, and its surface is finished by the use of sandpaper or emery cloth, or by rubbing with suitable abrading materials in the form of fine granules or powder and of successively finer grades if need be, until a flat or egg shell finish be obtained; or if a highly polished surface is desired, butfing may be resorted to. The prominent and essential feature of my invention consists in the application to the cellulose com osition board or body, of a coating which is effective to prevent adhesion to contacting surfaces of a press. or pressure device when the formed body is subjected to pressure and heat, or when wrapped, packed, stored, or shipped.

By the method above set forth I produce an inexpensive insulating board or body of fine texture and great density, of high capacity of insulation against the passage of electric current, of any desired color, and of fine finish appropriate to varied uses.

The invention here set forth is intended primarily for the production of boards or slabs, but may be utilized in the production of bodies of various forms capable of being molded, dried, and compressed by apparatus suitable to such operation. The claims are intended to cover such bodies or roducts Whether in the form of boards, sla s, rods, bars, or other configuration, and are to be read with that understanding.

What I claim is 1. In the process of manufacture of electrical insulation boards or bodies having a base of cellulose with gilsonite or similar hinder, the steps, which consist in applying to the formed and dried body a surface coating of cellulose acetate varnish or lacquer; permitting the same to dry; and subjecting said body simultaneously toheat and pressure;

2. in the process of manufacture of electrical insulating boards or bodies having a base of cellulose with gilsonite or similar binder, the steps, which consist in applying to the formed and dried body a surface coating of cellulose acetate varnish or lacquer employing a suitable solvent; subjecting the body so coated simultaneously to heat and pressure; and finally cooling the same while maintaining the pressure; whereby said body is prevented from adhering to contactlng bodies or surfaces during subsequent treatment, or after completion.

3. In the process of manufacturing electrical insulation bodies having a cellulose base, the steps, consisting in adding to a cellulose acetate varnish or lacquer suitable coloring matter and coating therewith such portion or portions of the formed and dried cellulose body as is or are to, be exposed to heat and pressure in the process of complet ing said body; whereby such body is protected against adhesion to contacting surfaces during the process of completion, and the lacquer is caused to unite with the cellulose base and carry into the same the coloring matter.

4:. The herein described method of producing electrical insulation boards and bodies, which consists in the following steps: (1) forming a mass of pulp composi tion comprising cellulose and gilsonite or similar binder, and of the general form and dimensions to be given the finished product;

(2) removing from such mass its moisture content; (3) applying to any or all faces of the board or body so dried, a thin film or coating of cellulose acetate varnish or lacquer and permitting the same to dry; (4) subjecting the board or body after drying of the coating, to heavy pressure and to heat until the board or body is compacted to the desired density; (5) cooling the heated portions of the pressure device; and (6) relieving the board or body of pressure and removing it from the pressure device for final treatment or use.

5. The herein described method of producing electrical insulation boards and bodies, which consists in the following steps: (1) forming a mass of pulp composition comprising cellulose and gilsonite or similar binder, and of the general form and dimensions to be given the finished product; (2) removing from such mass its moisture content; (3) applying to any or all faces f the board or body so dried, a thin film or coating of cellulose acetate varnish or lacquer to which is added prior to its setting or drying a suitable pigment or coloring matter; (4) subjecting the board or body after drying of the coating to heavy ressure and to heat until the board or be y is compacted to the desired density; (5) cooling the heated ortions of the pressure device; and (6) re ieving the board or body of pressure and removing it from the pressure device for final treatment or use.

6. The herein described method of producing electrical insulation boards and bodies, which consists in the following steps: (1) forming a mass of pulp composition comprising cellulose and gilsonite or similar. binder, and of the general form and dimensions to be given the finished prodnot; (2) removing the moisture from such mass; (3) applying to any or all faces of the dried board or body a thin film or coating of cellulose acetate varnish or lacquer in which is incorporated a softening agent such as methyl ester of paratoluelsulphoneamide, and permitting the same to dry; (4) subjecting the board or body after drying of the coating, to heavy pressure and to heat until the board or body 1s compacted to the desired density; (5) cooling the heated portions of the pressure device; and (6) relieving the board or body of pressure and finally removing it from the pressure sonite or similar binder, dried and com-- pressed, and having incorporated in its outer surface or portion and united therewith, cellulose acetate varnish or lacquer.

8. As a new product or article of manufacture, an electrical insulating board comprising a body formed of cellulose and gilsonite or similar binder, dried and compressed, and having incorporated in its outer surface or portion and united therewith, cellulose acetate varnish or lacquer containing pigment or coloring matter.

9. As a new product or article of manufacture, an electrical insulating board or body, comprising a body formed of cellulose and gilsonite or similar binder, dried and compressed, and having incorporated in its exterior surface or portion and united therewith, cellulose acetatevarnish or lacquer and a softenin agent such as methyl ester of paratoluelsu phoneamide.

10. As a new product or article of manufacture, an electrical insulating board or body, comprising a body formed of cellulose and gilsonite or similar binder, dried and compressed, and having incorporated in its exterior surface or portion and united therewith, cellulose acetate varnish or lacquer containing pigment or coloring matter and a softening agent such as methyl ester of paratoluelsulphoneamide.

In testimony whereof I have signed my name to this specification.

DANIEL MANSON SUTHERLAND, Jr. 

